Solid state lasers are commonly used in field applications where the operating temperature may vary from minus 50° C. to plus 50° C. However, the stimulated emission cross section of the laser material depends on the temperature as described in M. Bass, L. Weichman, S. Vigil, and B. Brickeen, “The temperature dependence of Nd3+ doped solid-state lasers,” IEEE Journal of Quantum Electronics, vol. 39, pp. 741-748, (2003). Therefore, long pulse and active/passive Q-switched solid state lasers are temperature dependent. It has been assumed that the reflectivity of the mirrors in the laser resonators were independent of temperature since the laser mirrors are typically dielectric coatings and do not show a change in reflectivity with temperature in the range of approximately minus 50° C. and approximately plus 50° C. The only temperature dependent quantity in the output energy of the laser was considered to be the stimulated emission cross section.
Typically, prior art broad spectrum lasers were operated at the peak of the emission spectrum where the simulated emission cross section is the largest. These lasers vary dramatically in output as the operating temperature changes. The variations in output due to temperature make the temperature dependent lasers useless for applications in which the laser is operated in different climatic environments.
What is needed is a broad spectrum laser operating at wavelengths that are selected for temperature independent operation to solve this problem.